import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int minimumNumber(int n, String password) {
        // Return the minimum number of characters to make the password strong
        
        String numbers = "0123456789";
        String lowerCase = "abcdefghijklmnopqrstuvwxyz";
        String upperCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        String specialCharacters = "!@#$%^&*()-+";
        int nn = 0,  nlc = 0,  nuc = 0,  nsc = 0;
        char[] pc = password.toCharArray();
        for(int i=0;i<n;i++){
            if (numbers.contains(pc[i]+"")) nn++;
            if (lowerCase.contains(pc[i]+"")) nlc++;
            if (upperCase.contains(pc[i]+"")) nuc++;
            if (specialCharacters.contains(pc[i]+"")) nsc++;
        }
        int ret = 0;
        if (nn==0) ret++;
        if (nlc==0) ret++;
        if (nuc==0) ret++;
        if (nsc==0) ret++;
        
        return n>6 ? ret : Math.max(ret,6-n);
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String password = in.next();
        int answer = minimumNumber(n, password);
        System.out.println(answer);
        in.close();
    }
}